1. Field of the Invention
The present invention relates to a rolling stand and/or rolling station according to the characteristics of the pre-characterizing part of claim 1.
The present invention also relates to a rolling mill plant.
The present invention also relates to a rolling process.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Definitions
In this description and in the appended claims the following terms must be interpreted according to the definitions given in the following. In the present description the term “bar” indicates a general product of a metal material worked in the form of a product whose lengthwise development has much greater sizes than the sizes of the section of the product itself measured on a section taken on a plane orthogonal with respect to the line defining its lengthwise development. Although in the terminology generally used in the specific sector of rolling one makes a distinction between “bar”, “wire”, “wire rod” according to the diameter, or, in general, to the sizes in section of the product of metal material, in the present description the term “bar” is understood as also comprising the products usually identified by the terms “wire” and “wire rod”, that is to say, in general for the aim of the present description, comprising all the metal products obtained through a rolling process which may be rolled into bobbins or coils, or cut with an established length, packaged, and made available for the final use or for following working processes.
The expression “profile” of a bar indicates the shape of the bar along one of its orthogonal sections at its lengthwise development. Although in the description explicit reference is made to bars of a circular profile, the expression “profile” also means shapes other than circular, such as oval, elliptic, quadrangular, square, hexagonal shape, flat, band or sheet, “L”-shape, “C”-shape, “H”-shape, etc. It will be evident, in the light of the following description, that the present invention is applicable to a profile corresponding to a generic section, with minimum corrections that will be clear to a person skilled in the art. The term “bar” should be understood as also comprising different shapes in section as in the mentioned examples or other shapes suitable to be obtained by rolling.
In general one will use the expression “oblong metal material” to indicate said bars of any size in section, of any profile.
By the expression “rolling” one aims at indicating both hot rolling processes and cold rolling processes and by “rolled product” or “oblong metal material” one means a product resulting from rolling, both hot rolling and cold rolling.
The expressions roll/s and/or cylinder/s must be understood as substantially equivalent, as they are rotating elements of a cylindrical shape suitable for the mechanical working of the rolled product, which mechanically work the rolled product. The rolled product is made advance through a pair of rotating cylinders or rollers to undergo the mechanical deformation suitable to progressively reduce the thickness of the rolled product by means of a following passage in one or more rolling stations. Although in the embodiment illustrated the rollers or cylinders are represented as having a flat perimeter surface, by the expression rollers or cylinders one means to include also rollers or cylinders in which a first cylinder is provided with at least one first semi-channel and a second cylinder is provided with at least one second semi-channel, the reciprocal placing side-by-side of the cylinders involving the reciprocal placing side-by-side of the at least one first semi-channel and the at least one second semi-channel whose ensemble constitutes at least one rolling channel intended for the passage of the rolled product to be worked between said cylinders.
Prior Art
The oblong metal material in the form of bars is obtained, in general, from a production line that by means of rolling or extrusion processes brings about thermo-mechanical deformations on the metal material itself for the purpose of obtaining a bar with a determined profile and with determined sizes in section.
The production line, in general, comprises an initial portion of intermediate forging in which the oblong metal material of large sizes, usually indicated with billets, undergoes some initial treatments of thermo-mechanical deformation to turn it from a quadrangular section shape into an essentially round section shape. Afterwards, the production line includes an intermediate portion in which the oblong metal material generally, but not necessarily, undergoes successive thermo-mechanical deformations that turn it in sequence from essentially round section shapes into essentially ovoid section shapes with a progressive reduction in the size in section and extension of the oblong metal material. Finally, the production line includes one or more finishing portions intended to provide the oblong metal material with the final shape and sizes in section, if necessary with further working processes intended to obtain ribs or markings, division of the oblong metal material into two portions by means of “split lines”, etc. Each portion of the production line includes one or more working stations and in each of the working stations a working phase of the oblong metal material occurs, that is to say, a thermo-mechanical transformation. For example in a first working station of the intermediate portion of the production line there may be a deformation of the oblong metal material from an essentially round section shape to an essentially ovoid section shape with a reduction in the sizes in section, while in a second working station downstream of the first working station according to the direction of advancement of the material on the line there may be a deformation of the oblong metal material from an essentially ovoid section shape to an essentially round section shape with a reduction in the sizes in section. The process continues in the sequence of working stations until obtaining an oblong metal product with a determined size or surface area in section and a determined profile, which can be, for example, circular, ovoid or elliptic, quadrangular, hexagonal, “L”-shaped, “C”-shaped, etc.
The working stations generally include rolling stands with a vertical axis and with a horizontal axis. The rolling stands with a vertical axis include a pair of working cylinders whose rotation axis is on a vertical axis. The rolling stands with a horizontal axis include a pair of working cylinders whose rotation axis is on a horizontal axis. In general the oblong metal material is thermo-mechanically worked within a working groove obtained by approaching the two working cylinders, wherein a first semi-portion of the working groove is obtained on a first cylinder and a second semi-portion of the working groove is obtained on a second cylinder. For example in the case of a rolling stand that produces an oblong metal material with a round section, on the first cylinder a first groove portion of an essentially semicircular shape is obtained and on the second cylinder a second groove portion of an essentially semicircular shape is obtained symmetrical with respect to the first groove portion present on the first cylinder. Although in the present description and in the attached figures reference is mainly made to a configuration relating to a horizontal rolling stand, the present invention is also applicable to the case of rolling stands with a vertical axis, with minimum and obvious adaptations that will be immediately clear to those skilled in the art.
In the rolling lines of more recent technology, the rolling stands are made up of a fixed part that constitutes the working station and a removable and interchangeable part, called cartridge, which includes a supporting structure of the cylinders that are pivotally supported by means of support and rotation bearings, the cartridge further including mechanical control means for the change in the reciprocal distance or distance between centres between the two cylinders, that is to say, for the change in the opening or gap of the rolling channel. The same cartridge can be provided both as a cartridge for equipping rolling stands with a horizontal axis and as a cartridge for equipping rolling stands with a vertical axis, by means of the ninety-degree rotation of the body of the cartridge. The structure of the working lines without cartridges is similar except for the presence of a supporting removable and interchangeable part of the working cylinders. The present invention, although referred to the solution of rolling mill plants with removable and interchangeable cartridges, is applicable to both solutions.
In prior art the rolling cartridges (9) are operated by means of a control system (FIG. 16) made up of one single AC electric motor (25) at variable speed, operated by means of inverters, which usually has a maximum speed of 2000 rpm, a connecting toothed joint (26) between the motor and reducer, a speed reducer with two output shafts (27) with parallel or orthogonal axes, with two output shafts which rotate mechanically synchronized, two adapters (28) generally of the universal joint type connected to the rolling cylinders (31), an adapters supporting device (29), a rolling cartridge (9) provided with a pair of rolling cylinders (31) that are connected to the rolling cartridge through the linings, two adjusting reducers of the cylinders (30). The coupling between each cylinder (31) and the corresponding adapter (28) occurs by means of a hub or flange.
During the rolling of the oblong metal material, the rolling channel present on the rolling cylinders (31) wears out more or less rapidly according to the type of rolled material and to other process parameters. Following the wear, the rolling channel progressively widens giving rise to an increase in the size in section of the oblong metal material. In order to compensate for the wear of the channel it is necessary to use universal joints to compensate for the change in the section of the oblong metal material. When a rolling channel is so worn-out that its wear can no longer be compensated for, one can generally resort to another rolling channel obtained on the same rolling cylinder, next to that subject to wearing. This operation occurs by shifting the rolling cartridge in such a way as to bring the new rolling channel in correspondence of the rolling line of the rolling mill plant, which is fixed. In the case of the horizontal rolling stands this occurs by translating the rolling cartridge horizontally, while in the case of the vertical rolling stands this occurs by translating the rolling cartridge vertically. The cylinders (31) must be replaced periodically and, to facilitate and fasten the change operation, the whole stand can be disengaged being moved back, creating the conditions in which the whole group of rollers is extractable. In the case of the removable cartridges, on the other hand, they can be rapidly replaced as they are mobile on a system of rails, in such a way as to position in their place a cartridge already prearranged with the new cylinders. The connection between the neck of the cylinder and the hub of the universal joint is made by means of a shape coupling that is loose in such a way as to allow for the quick fitting of the cylinder on the hub. The hubs in this phase are supported by a mechanical device during the phase of change of the cylinders. As observed, the rolling cylinders can have several channels and, in order to be able to bring the desired rolling channel in correspondence of the rolling line of the plant, which is fixed, the flange holding carriage, too, must be mobile, horizontally in the case of the horizontal stands and vertically in the case of the vertical stands. The above applies to channels, but this reasoning must be extended also to other shapes and to the use of other rolls of different shapes including cylindrical shapes without rolling channels.
WO 98/32549 describes a rolling system, of the type comprising at least one pair of opposite rolling cylinders or rollers or rolls in which each rolling cylinder or roller is controlled directly by a respective motor, the rolling system comprising control means intended to modify, to coordinate the speeds of the motors operating on the rolling cylinders or rollers so that each pair of cylinders or rollers has the same rotation speed.
EP 1 247 592 describes a rolling mill that has a pair of upper and lower rollers intended to roll a metal band, and motors for driving the upper and lower rollers respectively. Between the upper roller and the upper driving motor and between the lower roller and the lower driving motor there are provided connection means with a diameter greater than the diameter of the cylinders. The upper driving motors are placed on opposite sides of the coupled cylinders.
In the solutions disclosed in WO 98/32549 and EP 1 247 592, the rolling cylinders and the motors are reciprocally connected by means of long adapters connecting the rolling station to the motors which are mounted on the ground at a long distance from the rolling station itself, the connection between the rolling cylinders and the motors occurring without the use of a gear reducer.
EP 2 221 121 describes a rolling mill for products in the form of plates or sheets that eliminates the rolling problems due to the deformation of the rolled material and to the flatness faults shaped with waves that develop in the width direction on the plate or sheet. The system provides the supply of a pair of upper and lower working cylinders, a pair of electric motors intended to control independently the pair of cylinders, control means for controlling an electric motor using the rotation speed of a cylinder as an objective control value and to control the other electric motor using the rolling torque applied to the rolled material by the working cylinder operated by said electric motor.
JPS5982103 describes a system for the rolling of products in the form of a relatively thick plate in a double-motor rolling mill, controlling the cylinder on the low speed side by means of the ratio of different speeds of cylinders on the sides at high and low speed. A motor for driving a cylinder on the high speed side always applies a rolling torque to a cylinder on the high speed side. A driving motor of a cylinder on the low speed side applies a rolling torque to a cylinder on the low-speed side when the ratio of different speeds of the cylinders of the high and low speed sides is lower than a required value and when said ratio is higher than the required value.
Problems of the Prior Art
The prior art solutions are particularly bulky to the extent that the rolling stands need considerable foundation works also considering the overall weight of the supporting structures of the rolling stands in which the rolling cartridges are inserted. As a consequence, also a plant with a reduced number of rolling passages needs a large space for its realization.
Furthermore, each rolling stand houses one single motor that, through a system of joints and reducers, controls both rolling cylinders installed on the cartridge, the motor having to be necessarily a motor of large sizes to be able to control both rolling cylinders and bear the rolling effort induced by the rolled product.
The mechanical transmission that is used to control the two rolling cylinders is complex and heavy.
Aim of the Invention
The aim of the present invention is to provide a rolling station with simplified mechanical transmission between the driving means of the rotation of the rolling cylinders and the rolling rollers or cylinders themselves.